Everything you want to (should) change is adjusted through System Preferences.
Now, there IS a UNIX command line available to you, but if you don't know what you're doing you can completely ruin the OS messing with some of the settings accessible that way.

From out there on the moon, international politics look so petty. You want to grab a politician by the scruff of the neck and drag him a quarter of a million miles out and say, "Look at that!" -...

However, as a general user and abuser, you shouldn't have a need to access EFI, most of the things done in BIOs on a PC is done via Disk Utility in your Applications>Utilities folder.

If your a coder, look into rEFIt, it will allow access and manipulation of the EFI to allow native booting from Linux, OS X and versions of Windows (need the drivers from Bootcamp naturally)

If you want to start a Mac from a OS X install disk (comes with your machine) and install OS X or replace the OS hold C while booting.

If you want to boot from a OS X install on another hard drive, hold Option while booting.

OS X has file permissions that need to be checked once in a blue moon or after a update or a install so they are correct. This is done in Disk Utility>repair permissions. File permissions is what gives Unix and Linux based operating systems it's great security.

If you want to repair, format, erase, replace OS X or partition your boot drive, you have to C boot from the installer disk, after a few screens the menu at the top will have a option to launch Disk Utility. This can also be done while Option booted from a OS X install on another hard drive. (warning: these methods can erase all data on your drives)

If you want to clone (or "Ghost" ) your whole boot drive to another hard drive, look for Carbon Copy Cloner (repair permissions in Disk Utility afterwards) then you can Option boot from a complete copy of your boot drive on another drive, very handy in emergencies or trying to restore. OS X does not have "restore points" as it rarely fails, but hard drives do fail and bad installs occur, so it's wise to keep a clone on standby and updated once in awhile.

Apple has TimeMachine built in OS X, which OS X will beg you to use when you hook up another drive and can restore your machine back from in case something happens to your boot drive, but requires a OS X install from the installer disks first on the boot drive. TimeMachine is not bootable like a clone is, so your machine is dead if your boot drive fails, but it's handy to restore earlier states of files, if you should so need too, most people just "Save As" and change the file like Revision B, C, D etc. The OS X installer disks just install the OS, can't use them to go on line to get help or use your computer like normal like a clone can. Some people use both methods, TimeMachine for file backups and another restore option and cloning the whole boot drive to another drive as a bootable method to get their computer working in seconds.

So perhaps a quick read of a book on OS X is in order before you proceed.

Mac's are computers, so if your already up to speed on PC's it shouldn't take you too long to learn how it's done on OS X.